Remove confusing 'while checking' note from opaque future type mismatches
Maybe I'm just misinterpreting the wording of the note. The only value I can see in this note is that it points out where the async's opaque future is coming from, but the way it's doing it is misleading IMO.
For example:
```rust
note: while checking the return type of the `async fn`
--> $DIR/dont-suggest-missing-await.rs:7:24
|
LL | async fn make_u32() -> u32 {
| ^^^ checked the `Output` of this `async fn`, found opaque type
```
We point at the type `u32` in the HIR, but then say "found opaque type". We also say "while checking"... but we're typechecking a totally different function when we get this type mismatch!
r? ``@estebank`` but feel free to reassign and/or take your time reviewing this. I'd be inclined to also discuss reworking the presentation of this type mismatch to restore some of these labels in a way that makes it more clear what it's trying to point out.
Modify primary span label for E0308
Looking at the reactions to https://hachyderm.io/`@ekuber/109622160673605438,` a lot of people seem to have trouble understanding the current output, where the primary span label on type errors talks about the specific types that diverged, but these can be deeply nested type parameters. Because of that we could see "expected i32, found u32" in the label while the note said "expected Vec<i32>, found Vec<u32>". This understandably confuses people. I believe that once people learn to read these errors it starts to make more sense, but this PR changes the output to be more in line with what people might expect, without sacrificing terseness.
Fix#68220.
Fix invalid float literal suggestions when recovering an integer
Only suggest adding a zero to integers with a preceding dot when the change will result in a valid floating point literal.
For example, `.0x0` should not be turned into `0.0x0`.
r? nnethercote
Only suggest adding a zero to integers with a preceding dot when the change will
result in a valid floating point literal.
For example, `.0x0` should not be turned into `0.0x0`.
Correct suggestions for closure arguments that need a borrow
Fixes#107301 by dealing with binders correctly
Fixes another issue where we were suggesting adding just `&` when we expected `&mut _` in a closure arg
Migrate mir_build's borrow conflicts
This also changes the error message slightly, for two reasons:
- I'm not a fan of saying "value borrowed, by `x`, here"
- it simplifies the error implementation significantly.
Consolidate two almost duplicated fn info extraction routines
Moves `extract_callable_info` up to trait selection, because it was being (almost) duplicated fully there for similar diagnostic purposes. This also generalizes the diagnostics we can give slightly (see UI test).
Suggestion for type mismatch when we need a u8 but the programmer wrote a char literal
Today Rust just points out that we have a char and we need a u8, but if I wrote 'A' then I could fix this by just writing b'A' instead. This code should detect the case where we're about to report a type mismatch of this kind, and the programmer wrote a char literal, and the char they wrote is ASCII, so therefore just prefixing b to make a byte literal will do what they meant.
I have definitely written this mistake more than once, it's not difficult to figure out what to do, but the compiler might as well tell us anyway.
I provided a test with two simple examples where the suggestion is appropriate, and one where it is not because the char literal is not ASCII, showing that the suggestion is only triggered in the former cases.
I have contributed only a small typo doc fix before, so this is my first substantive rustc change.
Emit a hint for bad call return types due to generic arguments
When the return type of a function call depends on the type of an argument, e.g.
```
fn foo<T>(x: T) -> T {
x
}
```
and the expected type is set due to either an explicitly typed binding, or because the call to the function is in a tail position without semicolon, the current error implies that the argument in the call has the wrong type.
This new hint highlights that the expected type doesn't match the returned type, which matches the argument type, and that that's why we're flagging the argument type.
Fixes#43608.
When the return type of a function call depends on the type of an
argument, e.g.
```
fn foo<T>(x: T) -> T {
x
}
```
and the expected type is set due to either an explicitly typed
binding, or because the call to the function is in a tail position
without semicolon, the current error implies that the argument in the
call has the wrong type.
This new hint highlights that the expected type doesn't match the
returned type, which matches the argument type, and that that's why
we're flagging the argument type.
Fixes#43608.
Migrate mir_build diagnostics 2 of 3
The first three commits are fairly boring, however I've made some changes to the output of the match checking diagnostics.
Fix invalid syntax and incomplete suggestion in impl Trait parameter type suggestions for E0311
Fixes#105544
The problems: The suggestion given for E0311 has invalid syntax when the synthetic type parameter is used for Trait type in function declaration:
```rust
fn foo(d: impl Sized) -> impl Sized
```
instead of explicitly specified like the following:
```rust
fn foo<T: Sized>(d: T) -> impl Sized
```
In addition to the syntax error, the suggestions given for E0311 are not complete when multiple elided lifetimes are involved in lifetime bounds, not all involved parameters are given the named lifetime in the suggestions. For the following test case:
```
fn foo(d: impl Sized, p: &mut ()) -> impl Sized + '_ {
(d, p)
}
```
a good suggestion should add the lifetime 'a to both d and p, instead of d only:
```
fn foo<'a>(d: impl Sized + 'a, p: &'a mut ()) -> impl Sized + '_ {
(d, p)
}
```
The Solution: Fix the syntax problem in the suggestions when synthetic type parameter is used, and also add lifetimes for all involved parameters.
